Each validation message is assigned to a message class. The FI-SL application component is delivered with message class K2 containing examples of validation messages.
Creating a Message Class
To create a message class, you should use the ABAP Workbench (Tools
® ABAP Workbench ® Development ® Programming environment ® Messages). You can edit messages with the validation editor, but a message class should first be created in the ABAP Workbench. For more information, see the Basis documentation in the SAP library (Basis Components ® ABAP Workbench ® ABAP User’s Guide ® Writing ABAP Transactions ® Handling Errors and Messages).The first time you define validations in the system, the system prompts you to assign a message class to the validation messages you define.
The message class must belong to a transportable, customer-specific development class. Otherwise these messages cannot be transported together with the validation.